Helicobacter pylori (H. pylori) infection is the most common cause of chronic gastritis in man, and it has been implicated as an etiological factor in the development of peptic ulcer disease. More recently, epidemiological studies have demonstrated that H. pylori is an independent risk factor for gastric cancer and that people infected with H. pylori have a 3-6 fold higher risk of developing this condition than non-infected persons. Progression from H. pylori-related superficial gastritis to atrophic gastritis with intestinal metaplasia is felt to be a precursor to gastric cancer development. Investigators have postulated that the natural progression of H. pylori-associated chronic gastritis is to atrophic gastritis, which may be prolonged or shortened by dietary factors. Diets rich in fruits and vegetables and low in starch and salt are associated with a decreased risk of gastric cancer. The presence of antioxidants in these diets has been postulated to be the factors responsible for the decrease in cancer risk. These diets are also high in polyunsaturated fat which, as opposed to saturated ft, has been shown to inhibit bacterial growth. Recent studies have confirmed that polyunsatuated hat will inhibit H. pylori (named as a Class I carcinogen with an estimated attributable risk of 50-60% for gastric cancer by the World Health Organization) growth in vitro. Therefore, agents which inhibit bacterial growth, i.e., polyunsaturated fats are likely to decrease the risk of cancer due to this carcinogen. Investigators for this project postulate that diets high in fruits and vegetables protect gastric cancer because of the bacterial static properties of polyunsaturated fats. Since antioxidants such as vitamin E are present in oils rich in polyunsaturated fat, they feel that they serve mainly as a marker for ingestion of these fats, and are not the primary agents protecting against gastric cancer. This grant proposes to document in a cross-sectional study, the indirect correlation between polyunsaturated fat ingestion and gastric bacterial load. In vitro studies will be performed to elucidate the extent to which polynsaturated fat will not only inhibit growth, but also inhibit cytotoxicity induced by adherence of this bacterium to human gastric epithelial cells. Confirming this hypothesis would be very important to areas of the world which have a high incidence of gastric cancer, since these areas have both a high incidence of H. pylori and a high rate of re-infection with this organism after successful antibiotic treatment. Knowledge that dietary intake rich in polyunsaturated fat will reduce gastric cancer risk is likely to be a cost-effective way of preventing this disease, since there is a vaccine available and antibiotic therapy is not practical in certain countries.